linux-kernel - Re: [RFC 1/2] irqchip: qcom: pdc: Introduce irq_set

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Message-ID: <68130578959b36d92b721131a9b35e94@kernel.org>
Date:   Thu, 12 Mar 2020 11:38:50 +0000
From:   Marc Zyngier <maz@...nel.org>
To:     Maulik Shah <mkshah@...eaurora.org>
Cc:     Stephen Boyd <swboyd@...omium.org>, bjorn.andersson@...aro.org,
        evgreen@...omium.org, mka@...omium.org,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        agross@...nel.org, linus.walleij@...aro.org, tglx@...utronix.de,
        dianders@...omium.org, rnayak@...eaurora.org, ilina@...eaurora.org,
        lsrao@...eaurora.org, linux-kernel-owner@...r.kernel.org,
        mkshah=codeaurora.org@...codeaurora.org
Subject: Re: [RFC 1/2] irqchip: qcom: pdc: Introduce irq_set_wake call

On 2020-03-12 11:33, Maulik Shah wrote:
> On 2/27/2020 6:39 AM, Marc Zyngier wrote:
>> Maulik,
>> 
>> I'd appreciate if you could Cc me on all irqchip patches.
> 
> Sure Marc, i kept you in Cc for V2 addressing stephen's comments.

Thanks. Make sure you use maz@...nel.org (I accidentally replied from
my personal address).

> 
>> 
>> On 2020-02-25 17:16, Stephen Boyd wrote:
>>> Quoting Maulik Shah (2020-02-21 03:20:59)
>>>> 
>>>> On 2/20/2020 7:51 AM, Stephen Boyd wrote:
>>>> 
>>>>     How are wakeups supposed to work when the CPU cluster power is 
>>>> disabled
>>>>     in low power CPU idle modes? Presumably the parent irq 
>>>> controller is
>>>>     powered off (in this case it's an ARM GIC) and we would need to 
>>>> have the
>>>>     interrupt be "enabled" or "unmasked" at the PDC for the irq to 
>>>> wakeup
>>>>     the cluster.
>>>> 
>>>> Correct. Interrupt needs to be "enabled" or "unmasked" at wakeup 
>>>> capable PDC
>>>> for irqchip to wakeup from "deep" low power modes where parent GIC 
>>>> may not be
>>>> monitoring interrupt and only PDC is monitoring.
>>>> these "deep" low power modes can either be triggered by kernel 
>>>> "suspend" or
>>>> "cpuidle" path for which drivers may or may not have registered for 
>>>> suspend or
>>>> cpu/cluster pm notifications to make a decision of enabling wakeup 
>>>> capability.
>> 
>> Loosing interrupt delivery in idle is not an acceptable behaviour. 
>> Idle != suspend.
> 
> Agree, we are not lossing it, but rather RFC v1 was keeping a
> requirement on drivers to keep wake
> enabled by calling irq_set_wake when the interrupt is routed via PDC,
> even after coming out of suspend.

An endpoint driver shouldn't have to know what interrupt controller it
is connected to. So your "when the interrupt is routed via PDC" is
not enforceable.

         M.
-- 
Jazz is not dead. It just smells funny...